How to measure the N.O. and N.C. of a photocell using a multimeter
Photoelectric switch (photoelectric sensor) is the abbreviation of photoelectric proximity switch. It uses the object to be detected to block or reflect the light beam, and the synchronous loop gates the circuit to detect the presence or absence of the object. Objects are not limited to metal, all objects that can reflect light can be detected. The photoelectric switch converts the input current into a light signal on the transmitter and emits it, and the receiver detects the target object based on the intensity or presence of the received light. Photoelectric switch smoke alarms are common in security systems and are often used in industry to count the number of movements of robotic arms.
Nowadays, many photoelectric switches have both normally open and normally closed outputs. Normally open and normally closed are the output states of the photoelectric switch when no object is sensed. This means that the photoelectric switch has a normally open output and a normally closed output when there is no action.
Distinguish whether the photoelectric switch is normally open or normally closed:
1. Single contact ones can be distinguished from the model parameters;
2. Many products provide two sets of normally open and normally closed contacts at the same time. You can see the logo on the switch;
3. You can use a multimeter to measure
Is the proximity switch normally closed or normally open?
1 . Three-wire DC24V inductive PNP type: Brown is connected to +24V, blue is connected to 0V.
The black test lead is connected to the red test lead of the DC voltage range of the digital multimeter, and the black test lead is connected to 0V.
At this time, the multimeter is normally closed when there is 24V voltage, but it is normally open when there is no 24V voltage.
2 . Three-wire DC24V inductive NPN type: Brown is connected to +24V, blue is connected to 0V.
Black is connected to the black test lead of the DC voltage range of the digital multimeter, and the red test lead is connected to +24V.
At this time, the multimeter is normally closed when there is 24V voltage, and it is normally open when there is no 24V voltage.
